The present invention relates to a manually guided implement having a tool performing a reciprocating up-and-down movement, in which the tool is driven by a motor over a connecting rod and a swing system guided in a cylinder connected to the housing of the implement.
In a known implement of the aforementioned kind, the tool is connected to the free end of a sleeve arranged for vertical reciprocation in a cylinder fixed to the housing of the impliment. A piston is axially guided in the sleeve and is linked to a connecting rod to be driven from a rotating motor over a gear unit and a crank. Springs abut with opposite ends respectively against opposite end faces of the piston and transverse members provided at opposite ends of the sleeve. During rotation of the motor, the piston is moved up-and down in the sleeve, whereby the sleeve is driven by the springs from the piston to carry out in the cylinder a sliding up-and-down movement. This movement of the sleeve is transmitted to a tool fixedly connected to an end of the sleeve, projecting beyond the cylinder.
In order to assure in the mentioned construction an exact movement of the piston, which is driven by the connecting rod, the cylindrical peripheral face of the piston must have a necessary minimum length to avoid canting of the piston and, furthermore, the guide sleeve for the piston must also have a sufficient length so that the guide sleeve even at a maximum stroke is still perfectly guided in axial direction.
The thus resulting large contact faces between the guide sleeve and the cylinder, on the one hand, and the guide sleeve and the piston, on the other hand, form relatively large friction faces, which cause corresponding large friction losses, thus lowering the efficiency of the implement. In addition, with the magnitude and number of the surfaces which glide against each other, which necessarily require a careful machining and a perfect surface finishing, the manufacturing costs for piston and guide sleeve will correspondingly increase.